The present invention relates to a wall unit with thermal and accoustic insulation.
A known wall unit of this kind is constructed as a composite panel for external walls. It consists of an external layer of plastics coated sheet metal, thermal insulation in the form of compression resistant foamed plastics and an inner layer which is connected with the outer layer by means of a frame. In order to make the composite panel permeable to vapour, the outer layer is provided with vertical cuts for the purpose venting and behind each cut a vapour permeable filling strip is arranged, the inner layer being made of vapour permeable material e.g. in the form of a plaster board. As a result of this, the depositing of moisture inside the composite panel or on the side of the inner layer facing the cavity is avoided, this being in accordance with German Pat. Specification No. 1121304.
Another known wall unit for external walls comprises two sheet metal panels of equal size and with angularly folded margins. The sheet metal panels engage around sealing strips by means of their margins, and are connected together by means of an insulating plate bonded between them, this being in accordance with German Pat. specification No. 1 241 085.
Since on heating or cooling, the air enclosed in the wall unit expands or contracts, forces exist between the opposite walls of the panel, and moreover, the moisture which is contained in the air in the wall unit is deposited on the walls when a drop in temperature occurs, resulting in damage to the insulation and giving rise to rusting. Moreover, in this construction the insulating effect is not high.
Essentially better insulating effects can be achieved with the use of reflecting metal foils. They enable an effective thermal protection but form an air and moisture-tight closure. On cooling down of the wall unit, moisture is deposited on the foils incorporated in the wall unit, so that their insulating action is considerably reduced and the moisture gradually reaches other regions of the wall unit. In this respect, reference is made to German patent specifications Nos. 870 751 and 706 545.
The present invention has the object of improving the thermal and accoustic insulation of wall units avoiding the depositing of moisture in them, and avoiding the production of forces between the walls of the wall unit with a change in ambient temperature.